1. Field of the Invention
The present invention relates to an exercise device for holding a bicycle rear wheel in order to produce a similar effect that of real bicycle racing. More particularly, the invention pertains to a apparatus for applying a controllable resistive load to the bicycle pedals.
2. Description of the Related Art Exercise devices that are set on the floor for holding the rear wheel of the bicycle are available on the market. These devices generally permit the user to obtain a similar exercise effect to that obtained by an actual racing bicycle.
A typical exercise device includes an apparatus for applying resistance to the rear wheel, proportionally to the rotating velocity of the rear wheel. The user's physical strength and health condition would enable the user to vary the resistance value.
A conventional loading apparatus has fans that generate variable air resistance on the pedals. This loading apparatus generates loud noise, and causes the fans to disturb and to spread the settled dust surrounding the exercise apparatus. Thus, the use of these conventional exercise device would generally be confined to areas that are regularly dusted and maintained. Additionally, these conventional exercise devices could not be efficiently used in wide open places, such as on the beach, where air draughts would counter act, and exert undesirable force on the fans spread of dust since the air is disturbed with the fans.
Another proposed loading apparatus includes a brake for engaging a rotary disk fixed on a shaft. The shaft is driven by the rear wheel of the bicycle. Therefore, the brake generates a frictional resistance that is proportional to the strenuousness of the user's exercise. However, this device uses frictional resistance. Therefore, the resistance of the brake decreases as the engaging portions become worn out, and will eventually result in the inability to adjust the desired resistance accurately. Also frequent maintenance is required for the brake which would require repeated replacement.
In order to solve these problems, U.S. Pat. No. 4,826,150, discloses an exercise device with a magnetic load resistive apparatus. As shown in FIG. 8, the load resistive apparatus includes a rotary shaft 63 which supports the bicycle. A rotary metal disk 60 is fixed to one end of the rotary shaft, and a pair of disks 61 are disposed on the opposite sides of the rotary disk 60. The rotary disk 60 includes a plurality of permanent magnets 62 that are concentrically arranged around the rotational axis of the disk 61. The rotation of the disk 60 and the magnetic flux of the opposite by disposed magnets 62, generate an eddy current. The resistive load, which is generated by the eddy current on the rotary disk, is transmitted to the rear wheel of the bicycle via the rotary shaft 63. By adjusting a control knob or adjusting handle, the permanent magnets 62 are circularly moved, thus changing the amount of the magnetic flux, which, in turn, adjusts the magnitude or value of the resistive load. The noise level generated by this magnetic load resistive apparatus is low since the resistive load is generated magnetically. Additionally maintenance need is reduced and facilitated, as minimal wear takes place. Moreover, the resistive load can be adjusted easily.
In the above loading apparatus, the position of the permanent magnets, on one side of the rotary disk, can be shifted to face the spaces formed between the permanent magnets on the other side of the rotary disk, because the intervals between the circularly shaped permanent magnets are equidistally spaced apart. The two sets of permanent magnets that are disposed on either side of the rotary disk are not aligned with one another. Consequently, the magnetic flux does not change linearly, but rather changes non-linearly as a function of the adjustment or displacement of the control knob, as illustrated in FIG. 9. Therefore, the magnetic flux and the load will change disproportional with the positional displacement of the control knob. It would also be difficult for the user to adjust the resistive load due to the non-linear relationship between the resistive load and the knob displacement. While the user would eventually learn to accurately control the resistive load, and in certain applications, the non-linear relationship is desirable, there remains a need for a new loading apparatus that is easily and quickly controlled by the majority of users.